Contents

Background

To improve performance, Mozilla saves a “compiled” version of the XUL and JavaScript to disk periodically so that it does not have to re-parse the data from chrome files on startup. This caching (often referred to as “XUL FastLoad” or just “FastLoad”) significantly decreases the time it takes to do a cold start of a Mozilla application.

The file to which the serialized data is saved differs by platform. On OS X it’s XUL FastLoad File; on Linux it’s xul.mfasl; and on Windows it’s XUL.mfl.